Radiopharmaceutical capsules, e.g., radioactive iodine capsules, are used, for example, in oncology, e.g., in the treatment of thyroid cancer. Because of their radioactivity, such capsules typically are stored and transported in resealable lead canisters or "safes." Previously, such safes have been constructed so that they are either closed, i.e., the radiopharmaceutical capsules is environmentally sealed and the radiation is contained within the safe, or open, i.e., the capsule is environmentally exposed and the radiation is no longer contained. With such safe configurations, the radiopharmaceutical capsule is environmentally exposed even when the capsule is only being assayed, i.e., the radioactive strength of the capsule is being measured by means of a Geiger counter or in an ionization chamber.